The present invention relates to pharmaceuticals, foods and beverages which are useful to pathogenic organisms due to their antiviral action.
In the antiviral action, there will be an action of inducing the resisting ability to virus such as inhibition of infection of virus to cells, inhibition of multiplication of virus in the infected cells, and the like, an action or selectively killing the cells which are infected by virus, and an action of inactivating (i.e., eliminating the infecting ability of) the virus itself.
There is a neutralizing antibody as a substance which has an action of inactivating the virus itself while there is vaccine as a means for inducing such an antibody. However, although the induction of the antibody by administration of vaccine is effective in preventing the infection of virus, effective therapeutic methods using antibody are rarely available at present. In addition, there is no effective therapeutic method in which virus is directly inactivated by pharmaceuticals.
With regard to action of inducing a resisting ability to virus, there will be inhibition of replication of genome of virus, inhibition of transcription of gene of virus, inhibition of synthesis of protein of virus, inhibition of folding of protein of virus, and the like. In inducing such actions, there will be suppression of activity or expression of transcription factor in the cell, suppression of activity or expression of transcription factor derived from virus, induction of heat shock proteins, and the like. An example of the substances which are capable of inducing such an action is prostaglandin.
Examples of the agents which selectively kill the cells which are infected by virus are acyclovir, ganciclovir, sorivudine, and the like which have been used as drugs against herpes virus.
Against virus, it is more effective to cope with by means of a synergistic action than by means of a single action. For example, even when a substance which selectively kills the virus-infected cells is administered, it is very difficult to completely eliminate the virus because, until the infected cells are killed, new virus is generated and other cells are infected by that. On the other hand, even when a substance which has an action of inducing a resisting ability to virus is. administered, it is not possible to eliminate the infected cells.
An object of the present invention is to develop the compounds which have a function of inducing a resistance to virus into cells and a function of selectively killing the virus-infected cells and to offer pharmaceuticals such as antiviral agent, agent for improving the hepatic functions, agents for inducing heat shock proteins, agents for preventing the carcinogenesis by oncogene, agents for preventing the chemical carcinogenesis, and the like and antiviral foods or beverages wherein the above-mentioned compound is contained.
The present inventors have conducted an intensive study for achieving such an object and have found that, when cells are treated with a compound which has a function of inducing a resistance to virus and of selectively killing the cells infected by virus, said virus-infected cells are selectively damaged and, therefore, amount of the virus which is generated until death of said cells decreases and that, since the cells which are not yet infected by virus acquire a resistance to virus due to administration of the compound, growth of the virus is suppressed even if it is newly infected. In other words, it has been found that the compound which has a function of inducing a resistance to virus into cells and of selectively killing the cells infected by virus is extremely effective for elimination of virus such as human AIDS virus or hepatitis C virus.
The function of the compound used in the present invention for inducing a resistance to virus into the cells can be measured by treating the compound to the cells prior to infection of virus followed by using inhibition of infection of virus to the cells, inhibition of replication of genome of virus, inhibition of transcription of gene of virus, inhibition of synthesis of protein of virus, inhibition of folding of protein of virus, and the like as the indexes or the yardsticks.
Further, the function of selectively killing the cells which are infected by virus can be measured by comparing the survival rate of the virus-infected cells with that of the uninfected cells.
There is absolutely no limitation for the compound having a function of inducing a resistance to virus into cells and also of selectively killing the cells infected by virus so far as said compound has both of those functions.
Now the present inventors have found 4,5-dihydroxy-2-cyclopenten-1-one represented by the formula [I] (hereinafter, just referred to as xe2x80x9cthe cyclopentenonexe2x80x9d) or an optically active compound or a salt thereof as the compound having a function of inducing a resistance to virus into cells and also of selectively killing the cells infected by virus whereupon the present invention has been achieved.
Outline of the present invention is that the first feature of the present invention relates to an antiviral agent which is characterized in containing at least one compound selected from a group consisting of 4,5-dihydroxy-2-cyclopenten-1-one represented by the following formula [I] and an optically active substance and a salt thereof as an effective component. 
The second feature of the present invention relates to antiviral food or antiviral. beverage which is characterized in containing at least one compound selected from a group consisting of 4,5-dihydroxy-2-cyclopenten-1-one represented by the formula [I] and an optically active substance and a salt thereof as an effective component.
In a preferred embodiment of the present invention, examples of the virus are human AIDS virus and hepatitis C virus. Examples of the antiviral agent are antiviral agent for human being, antiviral agent for non-human animals (such as antiviral agent for domestic animals, domestic fowls, fish or shrimps) and antiviral agent for plants.